The Title 24 ACM Reference Manual, Explained
The Alternative Calculation Method (ACM) Reference Manual is the rulebook for performance compliance software. It says how the proposed and standard designs are built, what the software must report and how vendors prove accuracy. Since September 2026 one 2025 manual covers single-family, multifamily and nonresidential buildings.
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What is in it
The Energy Commission’s manual (CEC-400-2026-006-CMF) has eleven chapters: an overview, general modeling procedures, software test requirements, building descriptors for nonresidential, multifamily and single-family buildings, common data structures, documentation, CALGreen and a glossary. The descriptors give the acceptable inputs for the proposed design and the specification of the standard design. The September 2026 update merged the separate single-family manual into the same document.
Who it is for
It is written for software vendors and the analysts who run the programs. The Commission’s public domain program, CBECC, and every third-party program must follow it. Section 10-116 requires a vendor to pass the tests in it, and the Commission may update the manual without a formal rulemaking, no more than twice a year.
What it decides on a CF1R
For a new single-family building the proposed design must be at or under the standard design budget in source energy, efficiency long-term system cost and total long-term system cost. The manual also caps the peak cooling increase at 25 percent in zones 10 and 14, and 30 percent in zones 4, 8, 9, 11, 12, 13 and 15. For additions and alterations the measure is long-term system cost per square foot of conditioned floor area. Those rules, not the software’s own choices, are why two approved programs agree.
Related reading
Compliance software covers approval, the calculator question covers what you can run yourself and prescriptive versus performance covers when this route pays. The Joint Appendices hold the data the manual relies on, such as JA3.
More Title 24 Guides
- What Every California Homeowner Should Know About Title 24
- 12 Things to Know Before Ordering a Title 24 Report
- Title 24 Checklist: What to Have Ready Before You Order
- How to Read Your CF1R, Page by Page
- 15 Title 24 Mistakes That Trigger Plan Check Corrections
- How to Choose a Title 24 Consultant
Frequently Asked Questions
Rarely. It is a vendor and analyst document, and your consultant applies it. It helps if you want to see why a model treated a feature as it did.
No. The compliance manuals explain the code to designers and builders. The ACM Reference Manual sets the modeling rules for software.
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